In recent years, in the fields of various electronic devices, such as a semiconductor device, requiring fine processing, demands for high density and high integration of the devices are more and more increased.
In a semiconductor production process, a step playing an important role in forming a minute circuit pattern is a photolithographic step.
A current photographic step is performed principally by reduced (size) projection exposure but a resolution thereof is restricted by diffraction limit of light and is about ⅓ of a light source wavelength.
For this reason, the wavelength can be shortened by using an excimer laser or the like as an exposure light source, so that fine processing on the order of about 100 nm can be performed.
Thus, lithography is advanced in level of the fine processing but with a shorter light source wavelength, is accompanied with many problems such as an increase in size of a device, development of a lens in an associated wavelength region, a device cost, a corresponding resist cost, etc.
Further, in recent years, the following devices requiring a high density hole array pattern or dot array pattern have been proposed.
A single electronic device has been disclosed in Japanese Laid-Open Patent Application (JP-A) 2001-168317, patterned media have been disclosed in JP-A 2005-190624, and a chemical sensor has been disclosed in JP-A 2003-268592. Further, a quantum dot laser device and a photonic crystal optical device have also been proposed.
However, these devices require higher precision fine processing technique than the semiconductor device, so that it is difficult to produce these devices in volume by the conventional lithographic technique.
On the other hand, as a cost-reduced and simple fine processing technique in place of the conventional lithographic technique, a method of arranging fine particles in a self-organizing manner or a method utilizing a microphase-separated structure formed by a block polymer has been reported.
Further, in recent years, a combined technique of the lithography with the self-organization has also been proposed. More specifically, Nature, 422, 411 (2003); Science, 308, 1442 (2005); and Nano Letters, 5, 1379 (2005) have disclosed that a chemically active group is formed in a pattern on a substrate and a minute pattern is formed by utilizing an interaction of the chemically active group with a block polymer.
These documents specifically disclose the following method.
By using, as a mask, a line-and-space resist pattern formed by lithography using extreme-ultraviolet (EUV), oxygen plasma ashing of an underlying substrate is performed. Then, at a surface of the substrate, a chemically active pattern comprising a hydrophilic portion and a hydrophobic portion is formed. Thereafter, the resist pattern is removed and then on the substrate, a block polymer having a polymethyl mathacrylate segment as a hydrophilic block and a polystyrene segment as a hydrophobic block is developed. Then, a regular phase-separated structure (a pattern having a hydrophilic block area and a hydrophobic block area) of the block polymer regulated by the chemically active pattern at the substrate surface is formed. In this method, a line-and-space pattern with a period of 47.5 nm or a hole pattern with a period of 55 nm is formed. In the case where the above described block polymer is developed on a substrate on which no chemically active pattern is formed, a disordered lamella pattern is formed.
In the method described in the above mentioned documents, the pattern of the chemically active group is formed at the substrate surface. For this purpose, a photolithographic step using a resist is required. That is, steps of resist application, baking, pattern exposure, and development are needed, thus being increased in the number thereof. For this reason, simplification of the steps is desired.